Abstract:
BACKGROUND : Modern molecular-based approaches for the detection of Mycobacterium tuberculosis in sputum
samples promise quicker and more accurate detection of cases. However, processing sputum samples at central
diagnostic facilities provides a diagnostic approach, but requires a safe and efficient system that is not affected
by transport delays and ambient temperature to be feasible. We evaluated the technical properties of
PrimeStore®-Molecular Transport Medium(PS-MTM) for its ability to inactivate mycobacteria, ensuring stability
of DNA over time at ambient temperatures and to assess the compatibility of the transport medium with DNA
extraction systems.
METHODS : Assessment of the transport medium for application of sputum samples processed for the detection of
M. tuberculosis included the inactivation of M. tuberculosis in spiked sputum samples, compatibility of the
medium with three commercial nucleic extraction systems and stability of DNA in the medium at ambient
temperature over 28 days. We further performed a clinical laboratory evaluation on 256 sputum specimens
sent for tuberculosis investigation.
RESULTS : Complete inactivation ofM. tuberculosis occurredwithin 30 min of exposure at a ratio of 1:3 for sputumto
PS-MTM. Sputum specimen in PS-MTMshowed very good compatibility with automated bead-based extraction
systems, producing high DNA output (estimated lower limits of detection: ~170 CFU/ml). Furthermore, PS-MTM
samples remained stable over 28 days at ambient temperature displaying no significant change over time in Ctvalues
(b5% on a mean starting value of 22.47). Of the 256 clinical sputumspecimens, 10.2%were culture positive
and 11.0% were positive by real-time PCR of PS-MTM samples.
CONCLUSIONS : Collecting and transporting sputum from TB suspects in PS-MTM offer safe transport at ambient
temperature, DNA stability for extended periods without cooling and specimens directly suitable for molecular
testing. This novel approach may support introduction and further scale-up of molecular diagnostics for TB in
resource-limited settings.
